Ni47Ti44Nb9合金相变及拉伸变形行为

利用电阻法和不同温度下的系列拉伸研究了Ni_(47)Ti_(44)Nb_9合金的相变及拉伸变形行为。结果表明:合金的拉伸变形行为强烈地依赖于拉伸变形温度。在Ms点以下,发生马氏体变体的再取向,其临界屈服应力随温度降低出现一极小值,在Ms和M_s~δ温度区间,应力诱发马氏体相变,其临界屈服应力随温度升高而降低。在略高于M_s~δ温度,延伸率出现一极小值,而在M_s~δ和Ms之间延伸率出现一极大值。形变使马氏体的逆相变点显著升高。     

Cu对304奥氏体不锈钢应变诱发马氏体相变的影响

借助 X-射线衍射分析法研究了 0.45% ~1.44%Cu 对(%)：0.068 ~ 0.072C 18.72~19.06Cr 、9.40~ 9.46Ni的304不锈钢-196 ℃低温拉伸应变诱发马氏体相变的影响。结果表明,Cu对304不锈钢-196 ℃应变诱 发e马氏体相变有明显的抑制作用;当Cu含量增至1.44%时,在经低温变形的钢中未检测到ε马氏体相变。随钢中Cu含量增加,-196℃ 应变诱发α'马氏体相变倾向降低,致使应变累积到一定程度后,流变应力低于低Cu钢。     

Ti-Ni形状记忆合金的疲劳性能

Ti- Ni形状记忆合金 (SMA)具有形状记忆效应和超弹性 ,其特性源于热弹性马氏体的形成和回复过程 ,相变过程的诱发需要温度或载荷变化。SMA要经历多次热应力或外加载荷循环作用 ,疲劳性能非常重要 ,其主要影响因素如下 :(1)合金马氏体相变开始温度 (Ms)。Ms不同导致合金相变过程和内部组织形态不同 ,疲劳寿命也不同。调整 Ni- Ti合金中 Ni含量 ,制备了 Ms 分别为 - 12 0℃ ,- 30℃ ,7.5℃和 70℃的合金。在室温下进行恒应变控制的疲劳试验。S- N曲线表明 :在应变相同的条件下 ,Ms 为 7.5℃的试样疲劳寿命最长 ,- 30℃和 70℃的居中 ,-…     

热机械循环对Ti49.8Ni50.2形状记忆合金相变行为的影响

研究了热机械循环对Ti49.8Ni50.2形状记忆合金的回复应变RS、应力诱发马氏体的临界应力σM以及马氏体相变温度Ms和Mf的影响.实验结果表明: Ti49.8Ni50.2在热机械循环冷却过程中始终发生应力诱发B2→B19′马氏体相变.RS在第一次和第二次循环中分别获得最大值和最小值, 随着循环的继续进行又逐渐增加.RS在达到第二个极大值后又开始逐步减小.σM随着循环次数增加而迅速下降.Ms和Mf在前10次循环中无明显变化, 随着循环的继续进而升高.循环500次后, RS, σM以及Ms和Mf均达到稳定状态.循环引入的位错结构被认为是造成以上变化的主要原因.     

碳含量对淬火碳钢温变形流变行为的影响

目前关于变形温度、应变速率等因素对流变应力的影响有大量的研究报道,而对温变形条件下碳含量的增加对流变应力的影响规律还缺乏系统研究.基于此开展起始组织为马氏体的不同淬火碳钢温变形流变行为研究.结果表明,在较低温度和较高应变速率(600℃,0.1～1s-1)下,流变应力随碳含量的增加而增大;在较高温度和较低应变速率下(700℃,0.01～0.001 s-1),流变应力在高碳范围内呈下降趋势.碳的质量分数低于0.78％时,淬火碳钢温变形激活能随碳含量的增加而降低;碳的质量分数高于0.78％时,淬火碳钢温变形激活能随碳含量的增加而增加.在相同变形条件下,能量耗散效率最大值随着碳含量的增加呈增大趋势.     

低于Ms温度变形对等温贝氏体相变动力学和组织的影响

摘要：变形和等温热处理是高强贝氏体钢主要生产工艺,已有研究表明低于马氏体相变起始温度（Ms）的等温热处理可以促进贝氏体相变动力学,低温奥氏体预变形也可以加速贝氏体相变。研究了低于Ms温度变形对后续等温贝氏体相变动力学和组织的影响,结果表明,并未出现预想的加速相变叠加效应,反而,变形温度低于Ms温度时,贝氏体相变动力学减弱,等温贝氏体相变孕育期延长。低于Ms温度等温相变时,贝氏体铁素体与母相奥氏体位向关系接近K-S关系,变形试样虽然获得了一部分先马氏体,且能提高贝氏体形核率,但并非所有的胚核都能发生长大,变形改变母相奥氏体取向,使贝氏体原本的位向关系遭受破坏,导致有效形核率降低。     

临界退火中锰钢的组织性能和变形行为

 为了研究临界退火中锰钢的微观组织演变规律以及组织对力学性能和变形行为的影响,对冷轧中锰钢(0.1C-7Mn-0.35Si)在570～650 ℃范围内进行了临界退火处理。研究结果表明,随着退火温度升高,双相“奥氏体+铁素体”组织逐步趋于等轴化且晶粒有粗化的趋势,并且在650 ℃时出现了马氏体组织;试验钢的抗拉强度随温度升高而增加,而伸长率和屈服强度均呈下降趋势,局部不均匀变形带随着退火温度升高逐步弱化,在620和650 ℃时完全消失;在相对较高的退火温度下,粗化的等轴奥氏体晶粒中形变诱导马氏体相变的增强和大尺寸的铁素体晶粒中动态回复的减弱,以及更高温度时马氏体的引入等,均改善了屈服阶段的加工硬化能力,从而有效减弱或抑制吕德斯带的扩展。     

低温强变形奥氏体的马氏体相变

 研究了Fe 32%Ni合金在形变温度550 ℃、形变速率2×10-2 s-1的实验条件下，经过多道多向锻压变形后奥氏体的马氏体相变过程。采用电阻法、XRD分别研究了累积应变量对Ms点以及马氏体生成量的影响；采用TEM对形变位错密度以及马氏体组织进行了分析。结果表明：随着累积应变量的增大，奥氏体组织不断细化，深冷处理后马氏体生成量逐渐减少，Ms点逐渐降低，最终趋于恒定。原因是奥氏体的细晶强化以及形变位错的引入导致母相加工硬化抑制了马氏体形核，随着形变的累积，奥氏体的晶粒细化效果逐渐减弱，使得马氏体生成量减少的趋势也逐渐减弱，最终趋于恒定。     

温度与差应力对岩石熔融程度的等效关系——以角闪变粒岩为例

为了探讨差应力和温度与岩石熔融程度的关系,利用角闪变粒岩进行高温高压条件下的岩石变形实验.包括差应力条件下的动态实验,圈压100 MPa,温度700℃,施加相当于差应力为0～25 MPa,且以每5 MPa为间隔进行天然块状岩石样品的动态熔融;在相同的围压条件下,温度由700℃到900℃每50℃为间隔,进行无差应力条件下天然块状岩石的静态熔融实验,并进行对比研究.结果表明,在相同温度条件下,岩石的熔融程度随着差应力的增加明显增高.通过对斜率的对比分析表明:以700℃为基准,差应力每增加5 MPa.其带来的影响与温度升高40℃的效果相当,也说明中性岩石的熔融对差应力的敏感程度比酸性岩要高.     

AM对低碳贝氏体钢等温相变和显微组织的影响

摘要：设计了马氏体起始相变温度（Ms）以上和以下5个不同温度等温淬火实验,研究了Ms以上和以下温度等温淬火对低碳贝氏体钢组织和相变动力学的影响。结果表明,试样在Ms以下等温淬火时,保温前生成的先马氏体（AM）显著缩短了等温贝氏体相变孕育期,加速贝氏体形核,细化贝氏体组织。然而,Ms以下等温淬火时,总的等温贝氏体相变动力学与先马氏体的体积分数（fAM）有很大关系,当fAM较低时,AM的形成缩短了贝氏体相变孕育期,加速了贝氏体相变,当fAM过高时,又阻碍贝氏体相变,延长贝氏体总的相变时间。最后,采用Austin Rickett(AR)和Johnson Mehl Avrami Kolgomorov(JMAK)动力学模型对等温贝氏体相变动力学进行分析,结果表明,与AR模型相比,JMAK模型更适用于本研究的实验结果。     

A laboratory approach to the dynamics of psychological stress.

"This paper undertakes 2 somewhat limited tasks: (a) an analysis of some of the key problems in experimentation, and (b) the presentation of a brief account of some research from the author's own laboratory which was designed to throw light on some of the psychological mechanisms underlying stress reactions." Original research is summarized in 4 figures presenting the effect on skinconductance pattern of various conditions. The theoretical and methodological problems inherent in the field of psychological stress require attention to psychological processes (as well as the physiological) and the empirical conditions which identify these processes. "In the experimental laboratory what we need are more carefully thought out analogues of these psychological processes." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Stress reduction and prevention.

Reviews the book, Stress reduction and prevention edited by Donald Meichenbaum and Matt E. Jaremko (1983). In this edited volume, Meichenbaum and Jaremko extend the heuristic value of the stress management paradigm by having a number of researchers present their observations and programmes under the stress inoculation training umbrella. The organizational tactic is a success, as the book contains a wealth of theoretical and practical information dealing with stress management and prevention. The book is divided into three sections. The goal of the first section is to have the contributors survey the literature on stress and coping and to demonstrate the practical implications of their research. The second section of the book deals exclusively with the stress inoculation training paradigm. The third and final section represents the heart of the book. The reader is led through a number of interesting and novel applications of stress inoculation training. The editors are to be commended for this book--it is definitely worth purchasing (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural bases of moderation of cortisol stress responses by psychosocial resources.

Psychosocial resources have been tied to lower psychological and biological responses to stress. The present research replicated this relationship and extended it by examining how differences in dispositional reactivity of certain neural structures may underlie this relationship. Two hypotheses were examined: (a) psychosocial resources are tied to decreased sensitivity to threat and/or (b) psychosocial resources are associated with enhanced prefrontal inhibition of threat responses during threat regulation. Results indicated that participants with greater psychosocial resources exhibited significantly less cortisol reactivity following a stress task, as predicted. Analyses using functional magnetic resonance imaging revealed that psychosocial resources were associated with greater right ventrolateral prefrontal cortex and less amygdala activity during a threat regulation task but were not associated with less amygdala activity during a threat sensitivity task. Mediational analyses suggest that the relation of psychosocial resources to low cortisol reactivity was mediated by lower amygdala activity during threat regulation. Results suggest that psychosocial resources are associated with lower cortisol responses to stress by means of enhanced inhibition of threat responses during threat regulation, rather than by decreased sensitivity to threat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

金属成型过程中摩擦的分析

本文从微观入手对金属压力成型过程中摩擦的形成原因进行了分析,认为摩擦是由于变形金属被压入工具表面的凹坑所引起的。摩擦功率等于此部分金属的变形功率,当它的变形功率大于在界面产生剪切流动的功率时,摩擦由滑动转变为粘着摩擦。同时,根据对工具表面的某些假设,推导了摩擦应力与粗糙和静水压应力等之间的关系,并求出了发生粘着摩擦所需的静水压力。计算结果表明,建立的摩擦模型是比较有效和合乎实际的,它为理论计算摩擦     

A further study of the effect of stress on palmar prints.

In a recent publication, Mowrer has described a method for obtaining palmar prints. Presumably densitometer measurements of such prints vary directly with emotional upset and relaxation. This document describes a study that was designed to test directly the hypothesis that real-life stress can be related to the index of palmar sweat. All measurements were taken during a period of stress rather than during a temporally adjacent period. Briefly, the palmar prints of a group of 34 college students were taken during an examination and contrasted with control prints of the same Ss which were taken either two weeks prior to the examination or two weeks after the examination. The method utilized for taking the palmar prints was that described by Mowrer. The results are described. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

石油套管的壁厚公差对承载能力的影响

石油套管的强度计算是按API标准进行的，它未能反映高强度套管和尺寸公差对抗压溃能力的影响。利用弹塑性力学理论建立理想的石油套管的抗压溃能力计算公式，并考虑套管的壁厚公差对计算公式进行修正。用该方法对受均匀载荷及非均匀载荷作用的套管进行分析，并同有限元计算结果相比，两者十分吻合，说明该方法的有效性。     

计算机辅助齿轮试验台设计及关键零部件强度计算的软件开发与应用

系统介绍了齿轮试验的设备、测试方法以及试验方案,并对其优、缺点进行了阐述。通过比较并结合实际需求设计了合理的试验台结构,同时,对各部件的载荷工作状况进行了计算和校核。同时介绍了一种应用Delphi软件开发的计算齿轮接触应力的程序,用户可以通过输入一些设计参数来方便、快捷、准确的计算齿轮的接触应力并加以校核。     

厚壁冷成型钢构件残余应力分析

从理论上将厚壁冷弯残余应力形成过程模拟成大变形加载(弯曲)和弹性卸载(回弹)过程,对不同厚度、不同相对弯曲半径下的冷成型厚钢板进行了大变形弯曲和回弹分析,得到了弯曲应力场和回弹应力场,将这两种应力场相叠加,得到了残余应力场,并分析了其分布规律,最后以国外的实测结果为基础进行了比较分析,证实了该理论分析方法的正确性,从而为进一步研究残余应力对厚壁冷成型钢构件性能的影响奠定了理论基础。     

带钢淬火变形及硬度偏低原因浅析

针对带钢材料在淬火处理后出现的变形及硬度偏低的情况，从其生产工艺、化学成分，及金相组织方面，分析了其产生的原因，结果表明，造成此情况的原因是原材料的脱碳。     

不同应力状态下带钢的破鳞机理

利用自主设计的拉矫机对热轧带钢进行不同应力状态的破鳞试验,采用金相显微镜、扫描电镜和能谱分析对破鳞前后氧化皮的表面和界面进行分析,研究了带钢不同应力状态下的破鳞机理.试验结果表明,随着拉应力和压应力的增大,氧化皮全剥落率不断增大,并逐渐趋于稳定,且压应力的破鳞效果强于拉应力;拉应力作用下氧化皮以分层剥落为主,外层Fe3O4发生剥落,内层FeO仅在缺陷处发生少量剥落;而压应力作用下氧化皮以全剥落为主,临界弯曲应力随剥落量的增大而增大.